Heroin use and treatment admissions for heroin dependence have been increasing steadily. Clearly, there is a need for new effective treatments for opioid dependence. Buprenorphine, a long-lasting, partial agonist at the mu subtype of opioid receptor, is one of the most promising new maintenance medications for heroin dependence. Buprenorphine's advantages are that: (1) only mild withdrawal effects develop upon discontinuation of use; (2) it may retain its therapeutic effectiveness when administered on an alternate-day, rather than a daily, schedule; and (3) it is generally well-accepted by patients. Despite these advantages, research indicates that buprenorphine may have abuse liability. Although it is commonly believed that the abuse potential of buprenorphine is low, numerous countries have reported illicit diversion of buprenorphine and a growing population of buprenorphine abusers. To date, no laboratory studies have evaluated the abuse liability of buprenorphine in humans using a drug self- administration protocol, in which research volunteers are given the opportunity to take drug under controlled conditions. We are proposing to evaluate the abuse potential of buprenorphine in the laboratory, incorporating self-administration procedures with other measures of opioid effects. Physiological responses, subjects' verbal reports of drug effects, and learning and performance of a variety of computer tasks will also be measured. The studies will investigate the conditions under which buprenorphine may be self-administered in non- opioid-dependent individuals with a history of opioid abuse, as well as in opioid individuals. The aims of the proposed studies are to: (1) determine the conditions under which buprenorphine will serve as a reinforcer; (2) evaluate the abuse liability of the buprenorphine/naloxone combination, which is currently being developed to reduce illicit diversion of buprenorphine; (3) compare the reinforcing effects of buprenorphine with methadone, which is currently the most widely used maintenance medication for heroin dependence; and (4) assess buprenorphine self- administration in participants maintained on different doses of morphine. This research will furnish useful information for clinicians treating heroin abusers, and importantly, will provide information about the effects of buprenorphine on multiple measures of human functioning, as well as actual buprenorphine use.